Patent Application
20200217566
The present subject matter relates generally to mechano-caloric heat pumps for appliances.
Conventional refrigeration technology typically utilizes a heat pump that relies on compression and expansion of a fluid refrigerant to receive and reject heat in a cyclic manner so as to effect a desired temperature change or transfer heat energy from one location to another. This cycle can be used to receive heat from a refrigeration compartment and reject such heat to the environment or a location that is external to the compartment. Other applications include air conditioning of residential or commercial structures. A variety of different fluid refrigerants have been developed that can be used with the heat pump in such systems.
While improvements have been made to such heat pump systems that rely on the compression of fluid refrigerant, at best such can still only operate at about forty-five percent or less of the maximum theoretical Carnot cycle efficiency. Also, some fluid refrigerants have been discontinued due to environmental concerns. The range of ambient temperatures over which certain refrigerant-based systems can operate may be impractical for certain locations. Other challenges with heat pumps that use a fluid refrigerant exist as well.
Mechano-caloric materials (MECMs), e.g. materials that exhibit the elasto-caloric or baro-caloric effect, provide a potential alternative to fluid refrigerants for heat pump applications. In general, MECMs exhibit a change in temperature in response to a change in strain. The theoretical Carnot cycle efficiency of a refrigeration cycle based on an MECM can be significantly higher than for a comparable refrigeration cycle based on a fluid refrigerant. As such, a heat pump system that can effectively use an MECM would be useful.
Challenges exist to the practical and cost competitive use of an MECM, however. In addition to the development of suitable MECMs, equipment that can attractively utilize an MECM is still needed. Currently proposed equipment may require relatively large and expensive mechanical systems, may be impractical for use in e.g., appliance refrigeration, and may not otherwise operate with enough efficiency to justify capital cost.
Accordingly, a heat pump system that can address certain challenges, such as those identified above, would be useful. Such a heat pump system that can also be used in a refrigerator appliance would also be useful.
Aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.
In a first example embodiment, a mechano-caloric heat pump includes a mechano-caloric stage. An elongated lever arm extends between a first end portion and a second end portion. The elongated lever arm is pivotable about a point. A distance between the first end portion of the elongated lever arm and the point is less than a distance between the second end portion of the elongated lever arm and the point. A motor is operable to rotate a cam. The elongated lever arm is coupled to the cam proximate the second end portion of the elongated lever arm such that the motor is operable pivot the elongated lever arm about the point as the cam rotates. The elongated lever arm is coupled to the mechano-caloric stage proximate the first end portion of the elongated lever arm such that the motor is operable to stress the mechano-caloric stage via pivoting of the elongated lever arm as the cam rotates.
In a second example embodiment, a mechano-caloric heat pump includes a mechano-caloric stage. A first elongated lever arm extends between a first end portion and a second end portion. The first elongated lever arm is pivotable about a first point. A distance between the first end portion of the first elongated lever arm and the first point is less than a distance between the second end portion of the first elongated lever arm and the first point. A second elongated lever arm extends between a first end portion and a second end portion. The second elongated lever arm is pivotable about a second point that is spaced from the first point. A distance between the first end portion of the second elongated lever arm and the second point is less than a distance between the second end portion of the second elongated lever arm and the second point. A motor is operable to rotate a cam. The first elongated lever arm is coupled to the cam proximate the second end portion of the first elongated lever arm such that the motor is operable pivot the first elongated lever arm about the first point as the cam rotates. The second elongated lever arm is coupled to the cam proximate the second end portion of the second elongated lever arm such that the motor is operable pivot the second elongated lever arm about the second point as the cam rotates. The first elongated lever arm is coupled to the mechano-caloric stage proximate the first end portion of the first elongated lever arm and the second elongated lever arm is coupled to the mechano-caloric stage proximate the first end portion of the second elongated lever arm such that the motor is operable to stress the mechano-caloric stage via pivoting of the first and second elongated lever arms as the cam rotates.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Referring now to
Refrigerator 10 is provided by way of example only. Other configurations for a refrigerator appliance may be used as well including appliances with only freezer compartments, only chilled compartments, or other combinations thereof different from that shown in
The heat transfer fluid flows out of first heat exchanger 32 by line 44 to heat pump 100. As will be further described herein, the heat transfer fluid receives additional heat from caloric material in heat pump 100 and carries this heat by line 48 to pump 42 and then to second heat exchanger 34. Heat is released to the environment, machinery compartment 40, and/or other location external to refrigeration compartment 30 using second heat exchanger 34. A fan 36 may be used to create a flow of air across second heat exchanger 34 and thereby improve the rate of heat transfer to the environment. Pump 42 connected into line 48 causes the heat transfer fluid to recirculate in heat pump system 52. Motor 28 is in mechanical communication with heat pump 100 as will further described.
From second heat exchanger 34 the heat transfer fluid returns by line 50 to heat pump 100 where, as will be further described below, the heat transfer fluid loses heat to the caloric material in heat pump 100. The now colder heat transfer fluid flows by line 46 to first heat exchanger 32 to receive heat from refrigeration compartment 30 and repeat the cycle as just described.
Heat pump system 52 is provided by way of example only. Other configurations of heat pump system 52 may be used as well. For example, lines 44, 46, 48, and 50 provide fluid communication between the various components of the heat pump system 52 but other heat transfer fluid recirculation loops with different lines and connections may also be employed. For example, pump 42 can also be positioned at other locations or on other lines in system 52. Still other configurations of heat pump system 52 may be used as well. For example, heat pump system 52 may be configured such that the caloric material in heat pump 100 directly cools air that flows through refrigeration compartment 30 and directly heats air external to refrigeration compartment 30. Thus, system 52 need not include a liquid working fluid in certain example embodiments.
As may be seen in
A distance D1 between first end portion 326 of first elongated lever arm 322 and first point 330 is less than a distance D2 between second end portion 327 of first elongated lever arm 322 and first point 330. Thus, first elongated lever arm 322 is pivotable about first point 330 to provide a suitable mechanical advantage. As an example, the distance D1 may be no greater than half (½) of the distance D2. As another example, the distance D1 may be no greater than a quarter (¼) of the distance D2. As may be seen from the above, force applied at second end portion 327 of first elongated lever arm 322 is amplified at first end portion 326 of first elongated lever arm 322 via suitable selecting of the distances D1, D2.
Second elongated lever arm 324 also extends between a first end portion 328 and a second end portion 329, e.g., along the length of second elongated lever arm 324. Second elongated lever arm 324 is pivotable about a second point 340. For example, second elongated lever arm 324 may be mounted to an axle at second point 332. Second point 332 is spaced from first point 330. A distance D3 between first end portion 328 of second elongated lever arm 324 and second point 332 is less than a distance D4 between second end portion 329 of second elongated lever arm 324 and second point 332. The distances D3, D4 may be selected in the same or similar manner to that described above for the distances D1, D2 in order to provide a suitable mechanical advantage.
Mechano-caloric heat pump 300 also includes a motor 340, such as motor 28, that is operable to rotate a cam 342. First elongated lever arm 322 is coupled to cam 342 proximate second end portion 327 of first elongated lever arm 322. As an example, a roller 334 on second end portion 327 of first elongated lever arm 322 may contact and ride on cam 342. As another example, second end portion 327 of first elongated lever arm 322 may be directly connected to cam 342, e.g., via an axle. Second elongated lever arm 324 is coupled to cam 342 proximate second end portion 329 of second elongated lever arm 324. As an example, a roller 336 on second end portion 329 of second elongated lever arm 324 may contact and ride on cam 342. As another example, second end portion 329 of second elongated lever arm 324 may be directly connected to cam 342, e.g., via an axle. Due to the coupling of first and second elongated lever arms 322, 324, motor 340 is operable to pivot first elongated lever arm 322 about first point 330 and second elongated lever arm 324 about second point 332 as motor 340 rotates cam 342.
First and second elongated lever arms 322, 324 are also coupled to mechano-caloric stages 310, 312. For example, first elongated lever arm 322 is coupled to mechano-caloric stage 310 proximate first end portion 326 of first elongated lever arm 322, and second elongated lever arm 324 is coupled to mechano-caloric stage 312 proximate first end portion 328 of second elongated lever arm 324. Thus, motor 340 is operable to stress and/or deform mechano-caloric stages 310, 312 via pivoting of first and second elongated lever arms 322, 324 as motor 340 rotates cam 342. In particular, first and second elongated lever arms 322, 324 elastically deform as first and second elongated lever arms 322, 324 pivot on first and second points 330, 332, e.g., such that first and second elongated lever arms 322, 324 apply an elastic or spring force onto mechano-caloric stages 310, 312. The relatively large translation of first end portions 326, 328 of elongated lever arms 320 as elongated lever arms 320 pivot on first and second points 330, 332 may result in a relatively small translation of second end portions 327, 329 of elongated lever arms 320 and thus translation of a large force or pressure onto mechano-caloric stages 310, 312 as motor 340 rotates cam 342. As may be seen from the above, elastic deformation of elongated lever arms 320 and leverage may translate a large displacement at one end of elongated lever arms 320 into a large force with very low displacement at the opposite end of elongated lever arms 320.
Cam 342 is rotatable about an axis by motor 340. In
Mechano-caloric heat pump 300 may also include a fluid pump 346, such as pump 42, that is coupled to motor 340. Thus, motor 340 may drive both cam 342 and pump 346 in certain example embodiments. Pump 346 may be coupled to motor 340 via shaft 344 in certain example embodiments. Pump 346 is configured to flow heat transfer fluid through mechano-caloric stages 310, 312, heat exchangers 32, 34, etc., as discussed in greater detail below. Pump 346 may continuously flow the heat transfer fluid through mechano-caloric stages 310, 312. Alternatively, pump 346 may positively displace the heat transfer fluid through mechano-caloric stages 310, 312, e.g., in a periodic manner.
In
One or more of mechano-caloric stages 310, 312, 350 may include a mechano-caloric material, such as an elasto-caloric material, a baro-caloric material, etc. The mechano-caloric material may be constructed from a single mechano-caloric material or may include multiple different mechano-caloric materials, e.g., in a cascade arrangement. By way of example, refrigerator appliance 10 may be used in an application where the ambient temperature changes over a substantial range. However, a specific mechano-caloric material may exhibit the mechano-caloric effect over only a much narrower temperature range. As such, it may be desirable to use a variety of mechano-caloric materials within mechano-caloric stages 310, 312, 350 to accommodate the wide range of ambient temperatures over which refrigerator appliance 10 and/or an associated mechano-caloric heat pump may be used.
As noted above, mechano-caloric stages 310, 312, 350 include mechano-caloric material that exhibits the mechano-caloric effect. During deformation of mechano-caloric stages 310, 312, 350, the mechano-caloric material in mechano-caloric stages 310, 312, 350 is successively stressed and relaxed between a high strain state and a low strain state. The high strain state may correspond to when the mechano-caloric material is in compression and the mechano-caloric material is shortened relative to a normal length of the mechano-caloric material. Conversely, the low strain state may correspond to when the mechano-caloric material is not in compression and the mechano-caloric material is uncompressed relative to the normal length of the mechano-caloric material.
When the mechano-caloric material in mechano-caloric stages 310, 312, 350 is compressed to the high strain state, the deformation causes reversible phase change within the mechano-caloric material and an increase (or alternatively a decrease) in temperature such that the mechano-caloric material rejects heat to a heat transfer fluid. Conversely, when the mechano-caloric material is relaxed to the low strain state, the deformation causes reversible phase change within the mechano-caloric material and a decrease (or alternatively an increase) in temperature such that the mechano-caloric material receives heat from a heat transfer fluid. By shifting between the high and low strain states, mechano-caloric stages 310, 312, 350 may transfer thermal energy by utilizing the mechano-caloric effect of the mechano-caloric material in mechano-caloric stages 310, 312, 350.
As an example, working fluid may be flowable through or to stages 310, 312. In particular, with reference to
In addition, cool working fluid (labeled QH-IN) from second heat exchanger 34 may enter first stage 310 via line 50 when first stage 310 is in the low strain state, and the working fluid rejects additional heat to mechano-caloric material in first stage 310 as the mechano-caloric material in first stage 310 relaxes. The now cooler working fluid (labeled QC-OUT) may then exit first stage 310 via line 46, flow to first heat exchanger 32, and receive heat from refrigeration compartment 30.
Continuing the example, mechano-caloric stages 310, 312 may be deformed from the configuration shown in
In addition, cool working fluid QH-IN from second heat exchanger 34 may enter second caloric stage 312 via line 50 when second caloric stage 312 is in the low strain state, and the working fluid rejects additional heat to mechano-caloric material in second caloric stage 312 as the mechano-caloric material in second caloric stage 312 relaxes. The now cooler working fluid QC-OUT may then exit second caloric stage 312 via line 46, flow to first heat exchanger 32, and receive heat from refrigeration compartment 30.
The above cycle may be repeated by deforming first and second caloric stages 310, 312 between the configurations shown in
As may be seen in
Elongated outer and inner sleeves 410, 420 may be cylindrical. Thus, elongated outer sleeve 410 may have a circular cross-section along a length of elongated outer sleeve 410, and elongated inner sleeve 420 may also have a circular cross-section along a length of elongated inner sleeve 420. An outer diameter of elongated inner sleeve 420 may be selected to complement an inner diameter of elongated outer sleeve 410, e.g., such that friction between elongated outer and inner sleeves 410, 420 assists with mounting elongated inner sleeve 420 within elongated outer sleeve 410.
Mechano-caloric material 430 is disposed within elongated inner sleeve 420. Mechano-caloric stage 400 also includes a pair of pistons 440. Pistons 440 are received within elongated inner sleeve 420. Each of pistons 440 is positioned at a respective end of elongated inner sleeve 420. Thus, pistons 440 may be positioned opposite each other about mechano-caloric material 430 within elongated inner sleeve 420. Pistons 440 are moveable relative to elongated inner sleeve 420 and mechano-caloric material 430. In particular, pistons 440 may be slidable on elongated inner sleeve 420 in order to compress mechano-caloric material 430 between pistons 440 within elongated inner sleeve 420.
Seals 450, such as O-rings, may assist with limiting leakage of heat transfer fluid from within elongated inner sleeve 420 at the interface between elongated inner sleeve 420 and pistons 440. For example, a respective seal 450 may extend between each piston 440 and elongated inner sleeve 420. Each piston 440 may also include a roller 444. Rollers 444 may engage elongated lever arms 320 (
Elongated outer sleeve 410 also defines a pair of ports 412. Each port 412 may be positioned at a respective end of elongated outer sleeve 410. Thus, ports 412 may be positioned at opposite ends of elongated outer sleeve 410. Heat transfer fluid may enter and exit elongated outer sleeve 410 via ports 412.
Mechano-caloric material 430 may also define one or more channels 432 that extend through mechano-caloric material 430 along a length of mechano-caloric material 430. Heat transfer fluid may flow through mechano-caloric material 430 via channel 432 of mechano-caloric material 430. Each of pistons 440 may define a passage 442 that is contiguous with channel 432 of mechano-caloric material 430 and a respective one of ports 412. Heat transfer fluid from ports 412 may flow through pistons 440 via passages 442 and enter or exit channel 432 of mechano-caloric material 430. Thus, heat transfer fluid may flow through mechano-caloric stage 400 via ports 412, passages 442 and channel 432.
Mechano-caloric material 430 may be an elasto-caloric material when mechano-caloric material 430 is formed with channel 432, and the heat transfer fluid within elongated inner sleeve 420 may contact mechano-caloric material 430 in channel 432. Such direct contact between mechano-caloric material 430 and heat transfer fluid may improve heat transfer, e.g., relative to when the heat transfer fluid does not contact mechano-caloric material 430 in channel 432. It will be understood that mechano-caloric material 430 may include any suitable number of channels 432 in alternative example embodiments.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
